Bug 1980539 - Restrict -moz-symbolic-icon to Gecko. r=emilio,firefox-style-system-reviewers

This is a fixup for D252791, which added -moz-symbolic-icon as an image,
but Servo won't be using it.

Differential Revision: https://phabricator.services.mozilla.com/D259494

Author: Loirooriol

style/values/computed/image.rs

@@ -217,6 +217,7 @@ impl ToComputedValue for specified::Image {
             Self::Gradient(g) => Image::Gradient(g.to_computed_value(context)),
             #[cfg(feature = "gecko")]
             Self::Element(e) => Image::Element(e.to_computed_value(context)),
+            #[cfg(feature = "gecko")]
             Self::MozSymbolicIcon(e) => Image::MozSymbolicIcon(e.to_computed_value(context)),
             #[cfg(feature = "servo")]
             Self::PaintWorklet(w) => Image::PaintWorklet(w.to_computed_value(context)),
@@ -233,6 +234,7 @@ impl ToComputedValue for specified::Image {
             Image::Gradient(g) => Self::Gradient(ToComputedValue::from_computed_value(g)),
             #[cfg(feature = "gecko")]
             Image::Element(e) => Self::Element(ToComputedValue::from_computed_value(e)),
+            #[cfg(feature = "gecko")]
             Image::MozSymbolicIcon(e) => Self::MozSymbolicIcon(ToComputedValue::from_computed_value(e)),
             #[cfg(feature = "servo")]
             Image::PaintWorklet(w) => Self::PaintWorklet(ToComputedValue::from_computed_value(w)),

style/values/generics/image.rs

@@ -41,6 +41,7 @@ pub enum GenericImage<G, ImageUrl, Color, Percentage, Resolution> {
     /// A `-moz-symbolic-icon(<icon-id>)`
     /// NOTE(emilio): #[css(skip)] only really affects SpecifiedValueInfo, which we want because
     /// this is chrome-only.
+    #[cfg(feature = "gecko")]
     #[css(function, skip)]
     MozSymbolicIcon(Atom),
 
@@ -434,6 +435,7 @@ where
                 serialize_atom_identifier(selector, dest)?;
                 dest.write_char(')')
             },
+            #[cfg(feature = "gecko")]
             Image::MozSymbolicIcon(ref id) => {
                 dest.write_str("-moz-symbolic-icon(")?;
                 serialize_atom_identifier(id, dest)?;

style/values/specified/image.rs

@@ -253,6 +253,7 @@ impl Image {
             })?)),
             #[cfg(feature = "gecko")]
             "-moz-element" => Self::Element(Self::parse_element(input)?),
+            #[cfg(feature = "gecko")]
             "-moz-symbolic-icon" if context.chrome_rules_enabled() => Self::MozSymbolicIcon(input.expect_ident()?.as_ref().into()),
             _ => return Err(input.new_custom_error(StyleParseErrorKind::UnexpectedFunction(function))),
         }))